ESP32 Sleep modes

One of the biggest challenges within smart devices is maximizing the life of small, on-board batteries. In order to achieve longer battery life, engineers must make accurate battery drain measurements and understand the power consumption patterns. ESP32 is an excellent low-power SoC but it can be a relatively power-hungry device. I want to get an ESP32 to run for over 15 weeks on a single 1000mAh battery. To achieve this goal I am going try to explain one of the many possibilities of this SoC.

What is ESP32 sleep mode?

ESP32 Sleep mode is a power-saving state that ESP32 can enter when not in use. With the use of advanced power-management technologies, ESP32 can switch between different power modes.

• Power modes

Active mode: The chip radio is powered on. The chip can receive, transmit, or listen.

Modem-sleep mode: The CPU is operational and the clock is configurable. The Wi-Fi/Bluetooth baseband and radio are disabled.

Light-sleep mode: The CPU is paused. The RTC memory and RTC peripherals, as well as the ULP co-processor are running. Any wake-up events (MAC, host, RTC timer, or external interrupts) will wake up the chip.

Deep-sleep mode: Only the RTC memory and RTC peripherals are powered on. Wi-Fi and Bluetooth connection data are stored in the RTC memory. The ULP co-processor is functional.

Hibernation mode: The internal 8-MHz oscillator and ULP co-processor are disabled. The RTC recovery memory is powered down. Only one RTC timer on the slow clock and certain RTC GPIOs are active.

Power Consumption by Power Modes

Power mode	Description	Power consumption
Active (RF working)	Wi-Fi/BT Rx and listening	160 ~ 260mA
Modem-sleep	The CPU is powered on	20 ~ 68mA
Light-sleep	----	0.8 mA
Deep-sleep	RTC timer + RTC memory	10µA
Hibernation	RTC timer only	5µA
Power off	CHIP_PU is set to low level, the chip is powered off	0.1µA

Wake up from deep or lights leep modes can be done using several sources:

Timer
Touch pad
External wakeup(ext0 & ext1)

Timer Wake Up

RTC controller has a built in timer which can be used to wake up the chip after a predefined amount of time. The following function can be used to enable deep sleep wakeup using a timer esp_err_tesp_sleep_enable_timer_wakeup(uint64_t time_in_us)

Touch pad

You can wake up the ESP32 from deep sleep using the touch pins. You need to configure the touch pad interrupt before the chip starts deep sleep. The touch_pad_tesp_sleep_get_touchpad_wakeup_status(void) function can be used to enable this wake-up source.

External wakeup (ext0) and External wakeup (ext1)

The ext0 allows you to use a pin to wake up the chip esp_err_tesp_sleep_enable_ext0_wakeup(gpio_num_t gpio_num, int level)

The ext1 allows you to use multiple RTC GPIOs esp_err_tesp_sleep_enable_ext1_wakeup(uint64_t mask, esp_sleep_ext1_wakeup_mode_tmode)

Save Data on RTC Memories

You can save data on the RTC memories. The ESP32 has 8kB SRAM on the RTC part, called RTC fast memory. The data saved here is not erased during deep sleep or light-sleep mode. It is erased when you press the reset button. It is not possible to do dynamic allocation in RTC memory, but you can do static (compile-time) allocation. If you define a global variable with RTC_DATA_ATTR attribute, the variable will be placed into RTC_SLOW_MEM memory. Also you should be able to use RTC_DATA_ATTR with struct instances. For example : RTC_DATA_ATTR int counter = 0;

ESP32 Deep Sleep

In deep sleep mode, CPUs, most of the RAM, and all the digital peripherals which are clocked from APB_CLK are powered off. The only parts of the chip which can still be powered on are: RTC controller, RTC peripherals (including ULP coprocessor), and RTC memories (slow and fast). The chip consumes around 0.15 mA to 10µA. Along with the CPU, the main memory of the chip is also disabled. So, everything stored in that memory is wiped out and cannot be accessed. If you want to use the data over reboot, store it into the RTC memory by defining a global variable with RTC_DATA_ATTR attribute. esp_deep_sleep_start() function can be used to immediately enter deep sleep once wake-up sources are configured. By default, ESP32 will automatically power down the peripherals not needed by the wake-up source. Before entering deep sleep mode, applications must disable WiFi and BT using appropriate calls (esp_bluedroid_disable(), esp_bt_controller_disable(), esp_wifi_stop()). You have to remember something very important!!! When the ESP32 enters deep sleep, it turns off the processor that's running your code. The contents of memory and the current state of the processor are lost. So when it restarts out of deep sleep it's as if it just powered up. If you use Arduino as framework your setup() function will run again and will need to do any initialization again. Espressif IoT Development Framework is official development framework for ESP32. In this case your program will run from void app_main(void). But you have to know that ESP-IDF provides additional opportunities- ESP32 supports running a “deep sleep wake stub” when coming out of deep sleep. This function runs immediately as soon as the chip wakes up - before any normal initialisation, bootloader, or ESP-IDF code has run.

How to use

This example should be able to run on any commonly available ESP32 development board without any extra hardware.

Firstly, i declare my counter which counts each program restart.
I check if my program runs after sleep mode or not, i use the esp_sleep_get_wakeup_cause() function.
I define the wake up source by using the following function esp_sleep_enable_timer_wakeup(wakeup_time_sec * 1000000);
The esp SoC goes to sleep by calling the following function: esp_deep_sleep_start() You can look the my code within the following file...

Every time the ESP wakes up the counter variable increases. It also prints the wake up reason as shown in the figure below:

rst:0x1 (POWERON_��UQ�,boot:0x13 (SPI_FAST_F*M!}        OOT)
configsip: 0, SPR␕���5
clk_drv:0x00,q_drv'��0,d_drv:0x00,cs0_drv:0x�bB�}drv:0x00,wp_drv:0x00
m���DIO, clock div:2
load:��fff0018,len:4
load:0x3ff␖��␚�len:6284
load:0x40078��bb�n:10112
load:0x400804�bb��:6492
entry 0x4008075j
␛[0;32mI (28) boot: ESP-IDF 3.30300.190916 2nd stage bootloader␛[0m
␛[0;32mI (28) boot: compile time 20:04:59␛[0m
␛[0;32mI (29) boot: Enabling RNG early entropy source...␛[0m
␛[0;32mI (34) boot: SPI Speed      : 40MHz␛[0m
␛[0;32mI (38) boot: SPI Mode       : DIO␛[0m
␛[0;32mI (42) boot: SPI Flash Size : 4MB␛[0m
␛[0;32mI (46) boot: Partition Table:␛[0m
␛[0;32mI (49) boot: ## Label            Usage          Type ST Offset   Length␛[0m
␛[0;32mI (57) boot:  0 nvs              WiFi data        01 02 00009000 00006000␛[0m
␛[0;32mI (64) boot:  1 phy_init         RF data          01 01 0000f000 00001000␛[0m
␛[0;32mI (72) boot:  2 factory          factory app      00 00 00010000 00100000␛[0m
␛[0;32mI (79) boot: End of partition table␛[0m
␛[0;32mI (83) esp_image: segment 0: paddr=0x00010020 vaddr=0x3f400020 size=0x07d3c ( 32060) map␛[0m
␛[0;32mI (103) esp_image: segment 1: paddr=0x00017d64 vaddr=0x3ffbdb60 size=0x01ef4 (  7924) load␛[0m
␛[0;32mI (106) esp_image: segment 2: paddr=0x00019c60 vaddr=0x40080000 size=0x00400 (  1024) load␛[0m
␛[0;32mI (110) esp_image: segment 3: paddr=0x0001a068 vaddr=0x40080400 size=0x05fa8 ( 24488) load␛[0m
␛[0;32mI (128) esp_image: segment 4: paddr=0x00020018 vaddr=0x400d0018 size=0x14450 ( 83024) map␛[0m
␛[0;32mI (157) esp_image: segment 5: paddr=0x00034470 vaddr=0x400863a8 size=0x01f18 (  7960) load␛[0m
␛[0;32mI (160) esp_image: segment 6: paddr=0x00036390 vaddr=0x400c0000 size=0x00064 (   100) load␛[0m
␛[0;32mI (163) esp_image: segment 7: paddr=0x000363fc vaddr=0x50000000 size=0x00004 (     4) load␛[0m
␛[0;32mI (177) boot: Loaded app from partition at offset 0x10000␛[0m
␛[0;32mI (178) boot: Disabling RNG early entropy source...␛[0m
␛[0;32mI (184) cpu_start: Pro cpu up.␛[0m
␛[0;32mI (188) cpu_start: Application information:␛[0m
␛[0;32mI (192) cpu_start: Project name:     DeepSleep␛[0m
␛[0;32mI (198) cpu_start: App version:      1.0.0␛[0m
␛[0;32mI (202) cpu_start: Compile time:     Mar 25 2020 20:05:10␛[0m
␛[0;32mI (208) cpu_start: ELF file SHA256:  0000000000000000...␛[0m
␛[0;32mI (214) cpu_start: ESP-IDF:          3.30300.190916␛[0m
␛[0;32mI (220) cpu_start: Starting app cpu, entry point is 0x40080fd4␛[0m
␛[0;32mI (0) cpu_start: App cpu up.␛[0m
␛[0;32mI (230) heap_init: Initializing. RAM available for dynamic allocation:␛[0m
␛[0;32mI (237) heap_init: At 3FFAE6E0 len 0000F480 (61 KiB): DRAM␛[0m
␛[0;32mI (243) heap_init: At 3FFC0AA8 len 0001F558 (125 KiB): DRAM␛[0m
␛[0;32mI (250) heap_init: At 3FFE0440 len 00003AE0 (14 KiB): D/IRAM␛[0m
␛[0;32mI (256) heap_init: At 3FFE4350 len 0001BCB0 (111 KiB): D/IRAM␛[0m
␛[0;32mI (262) heap_init: At 400882C0 len 00017D40 (95 KiB): IRAM␛[0m
␛[0;32mI (269) cpu_start: Pro cpu start user code␛[0m
␛[0;32mI (287) cpu_start: Chip Revision: 1␛[0m
␛[0;33mW (287) cpu_start: Chip revision is higher than the one configured in menuconfig. Suggest to upgrade it.␛[0m
␛[0;32mI (291) cpu_start: Starting scheduler on PRO CPU.␛[0m
␛[0;32mI (0) cpu_start: Starting scheduler on APP CPU.␛[0m
Not a deep sleep reset
Enabling timer wakeup, 20s
Entering deep sleep
ets Jun  8 2016 00:22:57

rst:0x5 (DEEPSLEEP_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0018,len:4
load:0x3fff001c,len:6284
load:0x40078000,len:10112
load:0x40080400,len:6492
entry 0x40080750
␛[0;32mI (29) boot: ESP-IDF 3.30300.190916 2nd stage bootloader␛[0m
␛[0;32mI (29) boot: compile time 20:04:59␛[0m
␛[0;32mI (29) boot: Enabling RNG early entropy source...␛[0m
␛[0;32mI (35) boot: SPI Speed      : 40MHz␛[0m
␛[0;32mI (39) boot: SPI Mode       : DIO␛[0m
␛[0;32mI (43) boot: SPI Flash Size : 4MB␛[0m
␛[0;32mI (47) boot: Partition Table:␛[0m
␛[0;32mI (50) boot: ## Label            Usage          Type ST Offset   Length␛[0m
␛[0;32mI (58) boot:  0 nvs              WiFi data        01 02 00009000 00006000␛[0m
␛[0;32mI (65) boot:  1 phy_init         RF data          01 01 0000f000 00001000␛[0m
␛[0;32mI (73) boot:  2 factory          factory app      00 00 00010000 00100000␛[0m
␛[0;32mI (80) boot: End of partition table␛[0m
␛[0;32mI (84) esp_image: segment 0: paddr=0x00010020 vaddr=0x3f400020 size=0x07d3c ( 32060) map␛[0m
␛[0;32mI (104) esp_image: segment 1: paddr=0x00017d64 vaddr=0x3ffbdb60 size=0x01ef4 (  7924) load␛[0m
␛[0;32mI (107) esp_image: segment 2: paddr=0x00019c60 vaddr=0x40080000 size=0x00400 (  1024) load␛[0m
␛[0;32mI (111) esp_image: segment 3: paddr=0x0001a068 vaddr=0x40080400 size=0x05fa8 ( 24488) load␛[0m
␛[0;32mI (129) esp_image: segment 4: paddr=0x00020018 vaddr=0x400d0018 size=0x14450 ( 83024) map␛[0m
␛[0;32mI (158) esp_image: segment 5: paddr=0x00034470 vaddr=0x400863a8 size=0x01f18 (  7960) load␛[0m
␛[0;32mI (161) esp_image: segment 6: paddr=0x00036390 vaddr=0x400c0000 size=0x00064 (   100) ␛[0m
␛[0;32mI (164) esp_image: segment 7: paddr=0x000363fc vaddr=0x50000000 size=0x00004 (     4) ␛[0m
␛[0;32mI (178) boot: Loaded app from partition at offset 0x10000␛[0m
␛[0;32mI (179) boot: Disabling RNG early entropy source...␛[0m
␛[0;32mI (184) cpu_start: Pro cpu up.␛[0m
␛[0;32mI (188) cpu_start: Application information:␛[0m
␛[0;32mI (193) cpu_start: Project name:     DeepSleep␛[0m
␛[0;32mI (198) cpu_start: App version:      1.0.0␛[0m
␛[0;32mI (203) cpu_start: Compile time:     Mar 25 2020 20:05:10␛[0m
␛[0;32mI (209) cpu_start: ELF file SHA256:  0000000000000000...␛[0m
␛[0;32mI (215) cpu_start: ESP-IDF:          3.30300.190916␛[0m
␛[0;32mI (220) cpu_start: Starting app cpu, entry point is 0x40080fd4␛[0m
␛[0;32mI (0) cpu_start: App cpu up.␛[0m
␛[0;32mI (231) heap_init: Initializing. RAM available for dynamic allocation:␛[0m
␛[0;32mI (238) heap_init: At 3FFAE6E0 len 0000F480 (61 KiB): DRAM␛[0m
␛[0;32mI (244) heap_init: At 3FFC0AA8 len 0001F558 (125 KiB): DRAM␛[0m
␛[0;32mI (250) heap_init: At 3FFE0440 len 00003AE0 (14 KiB): D/IRAM␛[0m
␛[0;32mI (256) heap_init: At 3FFE4350 len 0001BCB0 (111 KiB): D/IRAM␛[0m
␛[0;32mI (263) heap_init: At 400882C0 len 00017D40 (95 KiB): IRAM␛[0m
␛[0;32mI (269) cpu_start: Pro cpu start user code␛[0m
␛[0;32mI (287) cpu_start: Chip Revision: 1␛[0m
␛[0;33mW (288) cpu_start: Chip revision is higher than the one configured in menuconfig. Suggest to upgrade it.␛[0m
␛[0;32mI (291) cpu_start: Starting scheduler on PRO CPU.␛[0m
␛[0;32mI (0) cpu_start: Starting scheduler on APP CPU.␛[0m
Wake up from timer. Time spent in deep sleep: 1500
Wake up from timer. The value of counter is: 1
Enabling timer wakeup, 20s
Entering deep sleep
ets Jun  8 2016 00:22:57

ESP32 Light sleep

In light sleep mode, digital peripherals, most of the RAM, and CPUs are clock-gated, and supply voltage is reduced, while RTC and ULP-coprocessor are kept active. This results in less power consumption than in modem sleep mode which is around 0.8mA(if modem is off, the chip should consume <1mA). ESP32 preserves its internal state and resumes operation upon exit from the sleep. Processor core is stopped, but can resume from same location in code. It is known Full RAM Retention. esp_light_sleep_start() function can be used to enter light sleep mode.

How to use

I define the wake up source by using the following function esp_sleep_enable_timer_wakeup(3000000);
The ESP SoC goes to sleep by calling the following function: esp_light_sleep_start();
The ESP SoC wakes up from sleep mode and i determine wake up reason. You have to remember that after chip was waked up, the program is executed from where it was last stopped, rather than restart. We can look console log for more information. You can look the my code within the following file...

��˙��ͥp: 0, *�]A�0�e��SH�HH���0� (POWQ���%UM␕T),boo����3 i␅␕}␙␅MQ_FLASH%==Q�      
cl�E���0x�,q_dr��x00,�E���0x�,cs0_���0x0bB�}����0x00,w�drv:0�0
mo�Y'T� ␚�ock dZ��j
l�X����f�␖���bb�n:4
�+��0x3��␖��␚�len:62�j
load'��007��0,leK�0112�!�+��0�00804�blen:�S�j
en��0x4��0750��␛[0;32mI (28) boot: ESP-IDF 3.30300.190916 2nd stage bootloader␛[0m
␛[0;32mI (28) boot: compile time 21:37:02␛[0m
␛[0;32mI (28) boot: Enabling RNG early entropy source...␛[0m
␛[0;32mI (34) boot: SPI Speed      : 40MHz␛[0m
␛[0;32mI (38) boot: SPI Mode       : DIO␛[0m
␛[0;32mI (42) boot: SPI Flash Size : 4MB␛[0m
␛[0;32mI (46) boot: Partition Table:␛[0m
␛[0;32mI (49) boot: ## Label            Usage          Type ST Offset   Length␛[0m
␛[0;32mI (57) boot:  0 nvs              WiFi data        01 02 00009000 00006000␛[0m
␛[0;32mI (64) boot:  1 phy_init         RF data          01 01 0000f000 00001000␛[0m
␛[0;32mI (72) boot:  2 factory          factory app      00 00 00010000 00100000␛[0m
␛[0;32mI (79) boot: End of partition table␛[0m
␛[0;32mI (83) esp_image: segment 0: paddr=0x00010020 vaddr=0x3f400020 size=0x07cdc ( 31964) map␛[0m
␛[0;32mI (103) esp_image: segment 1: paddr=0x00017d04 vaddr=0x3ffbdb60 size=0x01ef4 (  7924) load␛[0m
␛[0;32mI (106) esp_image: segment 2: paddr=0x00019c00 vaddr=0x40080000 size=0x00400 (  1024) load␛[0m
␛[0;32mI (110) esp_image: segment 3: paddr=0x0001a008 vaddr=0x40080400 size=0x06008 ( 24584) load␛[0m
␛[0;32mI (128) esp_image: segment 4: paddr=0x00020018 vaddr=0x400d0018 size=0x14438 ( 83000) map␛[0m
␛[0;32mI (157) esp_image: segment 5: paddr=0x00034458 vaddr=0x40086408 size=0x01f38 (  7992) load␛[0m
␛[0;32mI (165) boot: Loaded app from partition at offset 0x10000␛[0m
␛[0;32mI (165) boot: Disabling RNG early entropy source...␛[0m
␛[0;32mI (166) cpu_start: Pro cpu up.␛[0m
␛[0;32mI (170) cpu_start: Application information:␛[0m
␛[0;32mI (175) cpu_start: Project name:     LightSleep␛[0m
␛[0;32mI (180) cpu_start: App version:      1.0.0␛[0m
␛[0;32mI (185) cpu_start: Compile time:     Mar 26 2020 21:37:07␛[0m
␛[0;32mI (191) cpu_start: ELF file SHA256:  0000000000000000...␛[0m
␛[0;32mI (197) cpu_start: ESP-IDF:          3.30300.190916␛[0m
␛[0;32mI (202) cpu_start: Starting app cpu, entry point is 0x40080fd8␛[0m
␛[0;32mI (0) cpu_start: App cpu up.␛[0m
␛[0;32mI (213) heap_init: Initializing. RAM available for dynamic allocation:␛[0m
␛[0;32mI (219) heap_init: At 3FFAE6E0 len 0000F480 (61 KiB): DRAM␛[0m
␛[0;32mI (226) heap_init: At 3FFC0AA0 len 0001F560 (125 KiB): DRAM␛[0m
␛[0;32mI (232) heap_init: At 3FFE0440 len 00003AE0 (14 KiB): D/IRAM␛[0m
␛[0;32mI (238) heap_init: At 3FFE4350 len 0001BCB0 (111 KiB): D/IRAM␛[0m
␛[0;32mI (245) heap_init: At 40088340 len 00017CC0 (95 KiB): IRAM␛[0m
␛[0;32mI (251) cpu_start: Pro cpu start user code␛[0m
␛[0;32mI (269) cpu_start: Chip Revision: 1␛[0m
␛[0;33mW (270) cpu_start: Chip revision is higher than the one configured in menuconfig. Suggest to upgrade it.␛[0m
␛[0;32mI (273) cpu_start: Starting scheduler on PRO CPU.␛[0m
␛[0;32mI (0) cpu_start: Starting scheduler on APP CPU.␛[0m
Entering light sleep
Returned from light sleep, reason: timer, t=3017 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=6023 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=9028 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=12034 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=15040 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=18046 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=21051 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=24057 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=27063 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=30068 ms, slept for 3000 ms
Entering light sleep
Returned from light sleep, reason: timer, t=33074 ms, slept for 3000 ms
Entering light sleep

iqnev / esp32_sleep_modes

ESP32 Sleep modes

What is ESP32 sleep mode?

Power Consumption by Power Modes

Timer Wake Up

Touch pad

External wakeup (ext0) and External wakeup (ext1)

Save Data on RTC Memories

ESP32 Deep Sleep

How to use

ESP32 Light sleep

How to use

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